銭葵(ゼニアオイ) common mallow

花を乾燥させれば、青色のハーブティーが作れるそうです。道端でよく見かけますが、一度も試したことはありません。

I have heard that if you dry the flowers, you can make blue herbal tea. I often see it on the roadside, but I have never tried it.